The present invention relates to a magneto-resistive effect type head for reading an information signal from a magnetic medium and more particularly to a magneto-resistive effect type head having a structure capable of preventing the destruction of the insulation layer by static electricity.
With the down-sizing and performance improvement of the magnetic recording apparatuses in recent years, the magneto-resistive effect type head (hereafter referred to as the MR head) utilizing the magneto-resistive effect is used as the head for reading an information signal from the magnetic medium. FIG. 1 shows an example of the MR head. The MR head has a composite structure including a recording head 1 utilizing electromagnetic induction to write information and a reproducing head 2 utilizing a magneto-resistive effect (MR) or a giant magneto-resistive effect (GMR) to read the information signal from the magnetic medium.
FIG. 2 shows an example of the reproducing head in a view facing the magnetic medium. The reproducing head includes an MR sensor 30, electrode layers 40, a lower insulating layer 20, and an upper insulating layer 50, which are all disposed between a lower shield layer 10 and an upper shield layer 60. Generally, the bias layers 45 to apply a vertical bias magnetic field to the MR sensor 30 are provided on both sides of the MR sensor 30 (Normally, the bias layers and the electrode layer are formed successively).
The lower insulating layer 20 and the upper insulating layer 50 performs the function to magnetically and electrically isolate the MR sensor 30 from the lower shield layer 10 and the upper shield layer 60. As the material for the insulating layers, an aluminum oxide (alumina) film is generally used which is non-magnetic and superior in electrical insulating properties. The space where the MR sensor 30 is disposed between the lower shield layer 10 and the upper shield layer 60 is defined as a gap length GL. In a magnetic recording apparatus, the gap length GL is an important parameter related to bit length.